(a) Field of the Invention
This invention relates to novel compounds classified in the field of organic chemistry as 3-aryl- or 3-heteroaryl-3alkoxy-, phenoxy-, alkylthio- or phenylthiophthalides useful as color precursors, particularly in the art of carbonless duplicating, for example, pressure-sensitive and thermal marking systems, to processes for preparing the phthalides and to pressure-sensitive and thermal marking systems containing the phthalides.
(b) Description of the Prior Art
Several classes of organic compounds of widely diverse structural types are known to be useful as colorless precursors for carbonless duplicating systems. Among the more important classes, there may be named phenothiazines, for example, benzoyl leuco methylene blue; phthalides, for example, Crystal Violet Lactone; fluorans, for example, 2'-anilino-6'-diethylaminofluoran and 2'-dibenzylamino-6'-diethylaminofluoran; arylsulfinate salts of Michler's Hydrol; and various other types of colorless precursors currently employed in commercially-accepted carbonless copy systems. Typical of the many such systems taught in the prior art are those described in U.S. Pat. Nos. 2,712,507, 2,800,457, 3,041,289 and 4,000,087, which issued July 5, 1955, July 23, 1957, June 26, 1962 and Dec. 28, 1976, respectively. Many of the color formers in the prior art suffer one or more disadvantages such as low tinctorial strength, poor light stability, low resistance to sublimation, low susceptibility to copiability of the color-developed form in standard office copying machines, for example, a xerographic type of copier, and low solubility in common organic solvents, the latter disadvantage thus requiring the use of specialized and expensive solvents in order to obtain microencapsulated solutions of sufficient concentration for use in pressure-sensitive copying systems.
The following items to date appear to constitute the most relevant prior art with regard to the instant invention.
Newman and McCleary in the Journal of the American Chemical Society 63, 1537-1541 (1941) describe the preparation and physical characteristics of 3-phenyl-3-methoxyphthalide and an additional five phthalides bearing from one to three methyl substituents. These compounds were prepared by interacting in a first step 2-benzoylbenzoic acid or a methyl substituted derivative thereof with thionyl chloride with or without benzene to obtain the acid chloride. In a second step, the acid chloride was interacted with methanol in pyridine. No indication of utility for the compounds is given in the article.
Newman and Courduvelis in the Journal of Organic Chemistry 30, 1795-1800 (1965) described the preparation of 3-phenyl-3-methoxyphthalide and methyl homologs thereof from the interaction of 2-benzoylbenzoic acid and methyl alcohol under acid catalyzed conditions. No indication of utility for the compounds is given in the article.
Newman and Courduvelis in the Journal of the American Chemical Society 88, 781-784 (1966) describe the preparation of 3-phenyl-3-methoxyphthalide from the interaction of 2-benzoylbenzoic acid with methylchlorocarbonate in the presence of 1,4-diazabicyclo[2,2,2]octane. No indication of utility for the compounds is given in the article.
Newman and Lala in Tetrahedron Letters 34, 3267-3269 (1967) describe the preparation of 3-phenyl-3-methoxyphthalide from the interaction of 3-phenyl-3-chlorophthalide with methyl alcohol in the presence of various organic bases. No indication of utility for the compounds is given in the article.
Bhatt and Kamath in the Journal of the Chemical Society (B) 1036-1044 (1968) describe the physical characteristics of 3-phenyl-3-methoxyphthalide and phthalides substituted in the 3-phenyl with chloro, bromo, methyl, nitro and cyano moieties and their preparation from the interaction of the appropriate 2-(substituted benzoyl)benzoic acids with thionyl chloride and subsequent interaction of the acid chloride with methanol in the presence of an organic base. No indication of utility for the compounds is given in the article.